Scott, that is one gorgeous and well-grafted Adenium obesum tree!
If it were mine I would plant her in a decorative clay or ceramic container that is about the same depth but 2 inches wider. From my understanding and experience, grafted trees do not develop very large caudexes over time so it is fruitless to lift the caudex. When you do transplant, leave the root ball intact...just add more media at the bottom and the sides. The more feeder roots grafted plants have, the better they will give you a proliferation of blooms.
Just my two cents worth. Perhaps others with more experience could pipe in.
Note: If you choose a decorative clay pot, the interior of the pot needs to be painted with a compound of some kind to help keep the moisture from being absorbed by the clay...consequently drying out the media faster.
